1 A boy's catapult is made of rubber cord
which is 42 cm long, with 6 mm diameter
of cross-section and of negligible mass. The
boy keeps a stone weighing 0.02 kg on it
and stretches the cord by 20 cm by applying
a constant force. When released, the stone
flies off with a velocity of 20 ms -1 Neglect
the change in the area of cross-section of
the cord while stretched. The Young's
modulus of rubber is closest to:​